I did the same mod only more intensive- took a 2003 RF HU and Amp and put it into my 2001 SE.
Did not have a prob with security coding. All my probs were wiring related/ couldnt get the wiring harnesses and had to fab my own using wire diag from emanuals and cds. It was real fun trying to cram that Amp under the dash in the stock location. it finally went in but it was a bish.